Self piercing structural fastener having a working transition section

ABSTRACT

A fastener primarily intended for fastening a heavier gauge structural member to one or more members of lighter gauge. The fastener comprises a relatively small pilot point by virtue of which the fastener is self piercing with respect to the lighter gauge member or members to which the heavier gauge member will be fastened, an intermediate transition section immediately following the pilot point so as to stretch-extrude the initial hole to proper size, and a deep threaded body portion to anchor itself within the extruded hole. Preferably the working transition section is also threaded so as to lead the main body portion of the fastener into the pilot hole as enlarged by extrusion. The contour of the working transition section is such as to blend gradually into the larger main body portion of the fastener from the relatively small, self piercing pilot point.

United States Patent Sauer et al.

1451 May 13,1975

[ SELF PIERCING STRUCTURAL FASTENER HAVING A WORKING TRANSITION PrimaryExaminen-Edward C. Allen SECTION Attorney, Agent, or F irmMelville,Strasser, Foster &

Hoffman [75] Inventors: Gilbert F. Sauer, Franklin; Donald M. Taylor,Ross, both of Ohio [73] Assignee: Armco Steel Corporation, [57] ABSTRACTMlddletown Ohm A fastener primarily intended for fastening a heavier[22] Fil d; M 3, 1973 gauge structural member to one or more members oflighter gauge. The fastener comprises a relatively [211 App]' 356934small pilot point by virtue of which the fastener is self Related US. Ali ti D t piercing with respect to the lighter gauge member or [63]Continuation of Ser. No. [71,255, Aug. I2, 1971, members to which theheavier gauge member will be abandoned fastened, an mtermediatetransition section immediately following the pilot point so as tostretch-extrude 52 U.S. Cl 85/41; 85/46 the initial hole to Proper Size,and a p threaded 51 1m. (:1. F16b 25/00 body Portion anchor itselfWithin the extruded hole- [58] Field of Search 85/41, 46, 47 Preferablythe Working transition Section is also threaded so as to lead the mainbody portion of the [56] References Cited fastener into the pilot holeas enlarged by extrusion.

UNITED STATES PATENTS The contour of the working transition section issuch as to blend gradually into the larger main body portion gzffg 85/41of the fastener from the relatively small, self piercing 3:094:8956/l963 Broberg 85/47 plot FOREIGN PATENTS OR APPLICATIONS 2 Claims, 1Drawing Figure 1,150,769 4/l969 United Kingdom 85/46 7 C /6c 47 E fie /6F a /6b L 1 SELF PIERCING STRUCTURAL FASTENER HAVING A WORKINGTRANSITION SECTION CROSS REFERENCE TO RELATED APPLICATIONS ANDINVENTIONS This is a Continuation application of the copendingapplication Ser. No. 171,255, filed Aug. 12, 1971, and now abandoned, inthe name of the same inventors and entitled SELF PIERCING STRUCTURALFAS- TENER HAVING A WORKING TRANSITION SEC- TION.

BACKGROUND OF THE INVENTION 1. Field of the Invention The self piercingfastener of this invention is particularly suited for connecting heavierstructural members to lighter gauge members or panels. A supplementarynut may or may not be used. The fastener is completely self locatinginto a hole extruded in the lighter gauge panel in the region of thepierced hole initiated by the pilot point. This presents an optimumcondition for building connections.

2. Description of the Prior Art Although no formal search of the patentart has been made in connection with the invention herein shown,described and claimed, much of this art is known and has been reviewed.It would appear that the following United States patents are ofinterest. Johnson, U.S. Pat. No. 3,238,836; Hanneman U.S. Pat. No.3,125,923; Kahn U.S. Pat. No. 3,177,755; Rogers U.S. Pat. No. 413,968;Smith U.S. Pat. No. 3,357,295; Barth U.S. Pat. No. 2,703,419; HafertepU.S. Pat. No. 1,114,135; Haynes U.S. Pat. No. 2,388,482; Dewar U.S. Pat.No. 2,479,730; Broberg U.S. Pat. No. 3,094,895; Hanneman U.S. Pat. No.3,288,015; Lovisek U.S. Pat. No. 3,286,579; and Lindstrom U.S. Pat. No.3,094,893; Canadian Pat. No. 696,358 (Grossberndt) is also of interest.1

In general the known prior art fasteners rely on the removal of metal toenable the fastener to assume its final position. This requires anexpenditure of effort to produce the pressures required in order toeffect the connection and much time is consumed. Objects which areachieved by the fastener of the instant invention, therefore, are thespeedy installation of the fastener with a reduction in the pressurerequired to effect the connection. These results are made possiblelargely because the initial, pierced hole is enlarged by extrusionwithout the removal of additional metal.

SUMMARY OF THE INVENTION The fastener of this invention utilizes a pilotpoint the diameter of which is quite small in relationship to thediameter of the fastener body. This small pilot point removes a minimumof metal. The initial hole so produced is one enlarged by extrusion astretching of the metal. The fastener may be modified by arranging thethreads of the fastener body so as to achieve the maximum differentialbetween the major and minor diameters thereof. In some instances it maybe desirable to employ a nut in which case the nut is provided with aspecial mating thread; such a nut is usually employed only where maximumdesign requirements must be met. In most cases the relatively deepthreads of the main body portion of the fastener, cooperating with thehole as enlarged by the extrusion function of the transition section,are sufficient to effect the fastening desired. The heavy gauge memberwill be provided with a preformed clearance hole of sufficient diameterto permit the threaded fastener body to pass therethrough into the holeextruded in the lighter gauge metal by the working transition section ofthe fastener. This working transition section may also be threaded, evendeep threaded. In this case the major and minor diameters of thethreaded working transition section will taper from adjacent the pilotdrill point to the threaded fastener body, both of these diametersblending respectively with the major and minor diameters of such mainfastener body.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing comprises a single FIGUREshowing the fastener of this invention in position to fasten a heaviergauge member to two lighter gauge members; parts of the FIGURE are shownin section and others are diagrammatically illustrated by dotted lines.

DESCRIPTION OF THE PREFERRED EMBODIMENT The fastener of this inventionis generally indicated at 10. It comprises a washer head 11, a threadedfastener body 12, a working transition section 13 and a drill point 14.The fastener is shown as holding a heavy gauge structural member 15 totwo lighter gauge panels 16a and 16b. The nominal or major diameter ofthe fastener is indicated at 17 and the minor or root diameter of suchfastener is indicated at 18. The pitch dimension is indicated at 19. Thehole extruded in the light gauge panel is indicated at 20 and theclearance hole provided in the heavy gauge structural member isindicated at 21.

The diameter of the drill point 14 is relatively small and should notexceed about one-half the nominal or major diameter 17 of the fastenerbody 12. The minor or root diameter 18 of the fastener body 12 should beapproximately 1% times the diameter of the drill point 14. Thus theminor or root diameter 18 of the fastener body 12 should be about 66% orabout two-thirds of the major diameter 17. The pitch dimension 19 of thefastener body 12 should be sufficient to cooperatively receive the totalthickness of the light gauge panel or panels into which the fastener isthreaded, such total thickness including the extruded portion 160,whereby the extruded material will be in intimate contact with the rootdiameter 18 of the fastener body 12. As can be seen in the Figure theextruded portion strengthens the lighter gauge panel or panels in theregion of the hole 20 thereby increasing the resistance to the fastenerpulling out. The length of the transition section should not be lessthan the diameter of the drill point to provide a desirable entry angletherebetween for extruding the light gauge material. In those instanceswherein the working transition section 13 of the fastener 10 isthreaded, as is depicted in the drawing, the major and minor diametersof the threads of such transition section should,taper so as, movingfrom the drill point 14 to the fastener body 12, to blend with the majorand minor diameters l7 and 18 of such fastener body respectively.Portions of the tapered major and minor diameters of the workingtransition section 13 are indicated at 13a and 13b respectively.

From what has been said it will be observed that the fastener of thisinvention is designed with a relatively small pilot point and atransition section which extrudes a proper sized hole so as to lead themain body of the fastener into the pilot hole with minimum pressure. Thebody of the fastener may be deep threaded as illustrated to such extentthat the relationship of the major diameter and minor diameter will infact produce sufficient interference so that, within certain design loadlimit conditions, a nut is not required. If conditions so dictate,however, a nut having threads to mate with those of the body of thefastener may be employed.

The transition section, made up of the tapered threads 13a and taperedbody 13b, working in the small pilot hole pierced by the pilot drill,extrudes a hole of sufficient size to receive the threaded body portion12 of the fastener. Although such extrusion could be accomplished by thebody portion 13b alone, thus eliminating the tapered threads 13a, it hasbeen determined that best results are achieved when both of the taperedsections 13a and 13b are employed.

The precise configuration of the drill point 14 illustrated is notcritical except that it should fall within the limits indicated above.And it may be possible that the transition section could be some sort ofmetal removing section, such as a reamer, although it has been foundmuch more preferable to remove as little material as possible in thetransition from initial pierce to that hole size which willcooperatively receive the threaded body portion 12 of the fastener.Thus, for example, other known fasteners are generally smaller andemployed either to fasten light gauge materials to heavy gauge materialsor to fasten light gauge materials to light gauge materials; such otherfasteners, therefore, re move so much of the metal as to permit thefastener to pass through the hole with little interruption. Use of a nutis usually mandatory in those cases. This is not the kind of action andrelationship sought by practicing this invention in its preferred form.

In summary, the self piercing structural fastener incorporating theworking transition section of this invention removes a minimum amount ofmetal and to this end the diameter of the pilot point is small inrelationship to the nominal diameter of the fastener body. The hole soinitially pierced is then enlarged by the working transition sectionwhich stretch-extrudes the metal in the region of the pierced hole. Thethreads of the fastener body 12 should have a maximum differentialbetween the major and minor diameters thereof. A nut, especiallythreaded to mate with the threads of the fastener body 12, may beemployed in extreme conditions.

By enlarging the initially pierced hole without removing metal thepressure required to effect the connection of the heavy gauge metal tothe light gauge panel is reduced. Speedy installation is effected. Inthe preferred form of the invention, as illustrated, wherein the workingtransition section is itself threaded, with the tapers shown anddescribed, best results are achieved when these threads are relativelydeep and inclined. This affords maximum extrusion to the hole, thefastener body is thereby pulled into the hole with minimum pressure, andthe hole as so extruded, considering also the direction of extrusion,gives the optimum in thread engagement when the fastener body 12 entersthe extruded hole.

It will be apparent to those skilled in the art that modifications maybe made in this invention without departing from the scope and spiritthereof. Although the invention has been described and illustrated interms of certain structural elements, these are not to constitute alimitation on the claims except insofar as they are specifically setforth in them.

The embodiments of the invention in which an exclusive property orpriviledge is claimed are defined as follows:

l. A self piercing structural fastener, for fastening relatively heavygauge material to relatively light gauge material, comprising a threadedmain body having constant major and root diameters of the thread of saidthreaded main body, said root diameter being about two-thirds of saidmajor diameter, a drill point for initially piercing the light gaugematerial and the diameter of which drill point does not exceedapproximately one-half the said major diameter of the said threaded mainbody, a tapered and threaded working transition section extendingbetween said drill point and said main body, the length of saidtransition being at least the dimension of the said drill pointdiameter, the major and root diameters of the thread of said tapered andthreaded transition section increasing gradually and uniformly from thesaid drill point diameter throughout the said transition section so asto blend respectively with the major and root diameters of said threadedmain body, the said root diameter of said threaded main body beingapproximately one and onethird times the said diameter of said drillpoint, whereby said light gauge material is stretch-extruded as saidtransition section passes through the hole initially pierced by saiddrill point, and the pitch dimension of said threaded main body beingsufficient to cooperatively receive the total thickness of said lightgauge material as stretch-extruded by said transition section, wherebysaid stretch-extruded light gauge material will be in intimate contactwith the said root diameter of said main body, and whereby said fastenermay be passed through a preformed hole in said heavy gauge material ofgreater diameter than the major diameter of said main body and into thehole initially pierced in said light gauge material so that said mainbody may thread its way into said initially pierced hole asstretchextruded by said transition section speedily and with a minimumof pressure while achieving good holding power.

2. The fastener of claim 1 wherein said main body is surmounted by anintegral one-piece washer head.

l l l l

1. A self piercing structural fastener, for fastening relatively heavygauge maTerial to relatively light gauge material, comprising a threadedmain body having constant major and root diameters of the thread of saidthreaded main body, said root diameter being about two-thirds of saidmajor diameter, a drill point for initially piercing the light gaugematerial and the diameter of which drill point does not exceedapproximately onehalf the said major diameter of the said threaded mainbody, a tapered and threaded working transition section extendingbetween said drill point and said main body, the length of saidtransition being at least the dimension of the said drill pointdiameter, the major and root diameters of the thread of said tapered andthreaded transition section increasing gradually and uniformly from thesaid drill point diameter throughout the said transition section so asto blend respectively with the major and root diameters of said threadedmain body, the said root diameter of said threaded main body beingapproximately one and one-third times the said diameter of said drillpoint, whereby said light gauge material is stretch-extruded as saidtransition section passes through the hole initially pierced by saiddrill point, and the pitch dimension of said threaded main body beingsufficient to cooperatively receive the total thickness of said lightgauge material as stretch-extruded by said transition section, wherebysaid stretch-extruded light gauge material will be in intimate contactwith the said root diameter of said main body, and whereby said fastenermay be passed through a preformed hole in said heavy gauge material ofgreater diameter than the major diameter of said main body and into thehole initially pierced in said light gauge material so that said mainbody may thread its way into said initially pierced hole asstretchextruded by said transition section speedily and with a minimumof pressure while achieving good holding power.
 2. The fastener of claim1 wherein said main body is surmounted by an integral one-piece washerhead.